The object of these studies is to establish the general efficacy of the chemopreventive agent in a battery of In Vitro model systems representing different cell substrates. The studies are designed to distinguish between compounds that suppress initiation and promotion or both. Workstatement No. 39 The Contractor shall test and evaluate In Vitro Prescreening of Potential Chemopreventive Agents Using Biochemical Markers of the Carcinogenic Process. The objective of these studies is to prescreen selected potential chemopreventive agents and evaluate their activity by measuring transformation-associated biochemical endpoints. The assays selected are representative of several basic mechanisms thought to be associated with both the initiation and promotion processes of carcinogenesis. Positive activity in one or more of the assays would assist in the selection process for identifying compounds to be screened using longer term in vitro techniques.